Did you try the stock bass drum resonant head for a while before you put the ported one on?
Mine has a large amount of kickback on the pedal even though I don't have it tuned real tight.
I think there must be some really tight tolerances on these drums, or the air vent isn't large enough or something.
Seems like air can't escape, build up pressure and pushes back on the pedal. That's what it feels like anyways. I'm getting pretty used to it though.